Stability and Retention by DrNayAung

1. Sta bility and Retention
Nay Aung, BDS PhD
23.12.2022

2.  Orthodontic relapse is the term given when features of the original malocclusion return
following the active phase of treatment.
 Retention is the phase of treatment following active tooth movement that is aimed at
stabilizing corrected intra-arch and inter-arch relationships.
 Retention should be planned during the treatment planning stage and discussed in detail as
part of informed consent.
Stability and Retention

3.  Poor stability may occur for a number of reasons following treatment including:
 Periodontal recovery;
 Soft tissue imbalance;
 Skeletal growth.
Orthodontic stability

4.  Orthodontic tooth movement results in disruption of the periodontal and gingival structures.
 Because these tissues are slow to remodel following orthodontic tooth movement, residual
tension within the periodontal ligament and gingival fibers results in elastic recoil which
moves teeth toward their pre-treatment position.
 To prevent relapse, it is important to maintain the corrected positions until reorganization is
complete.
Orthodontic stability
(A) (i) the transseptal fibers (shown in red) are an
important cause of relapse of derotated teeth
because of the long interval required for the fibers
to reorganize following tooth movement.
(ii) Derotation results in stretching of the fibers with
generation of forces of elastic recoil.

5.  Following appliance removal, it takes approximately 3-4 months for the principal periodontal
fibers, 4-6 months for the gingival fibers and 1 year for the transseptal fibers to reorganize if
subjected to normal masticatory loading.
 Because of slow reorganization of the transseptal fibers, derotated teeth are particularly
prone to relapse and consideration should be given to long-term retention for severe
rotations.
 Pericision may help to reduce the relapse of derotated teeth in the short term, however, the
long-term benefits are questionable.
 This procedure involves surgically cutting the disrupted transseptal fibers by making a gingival
crevicular incision under local anesthesia following alignment.
Orthodontic stability

6.  If teeth are moved into an inherently unstable position during treatment, pressure from the
soft tissues, such as the lips, cheeks and tongue, may result in relapse.
 This may occur if the lower incisors are excessively (>2mm) advanced/proclined, if the dental
arches are expanded out of soft tissue balance, and if the upper incisors are not controlled by
the lower lip following incisor retraction (Class II cases).
 If such movements are undertaken intentionally, long-term retention should be planned at the
treatment planning stage and discussed as part of informed consent.
Orthodontic stability

7.  The skeletal growth pattern existing before orthodontic treatment is likely to continue
following appliance removal.
 This can result in a change in both inter-arch and intra-arch relationships.
 Vertical growth continues after the cessation of anteroposterior (AP) and transverse growth.
 Therefore, relapse in the vertical inter-arch relationship is more likely followed by
anteroposterior and transverse changes.
 Unfavorable growth can result in a relapse of overbite and overjet correction.
Orthodontic stability

8.  Skeletal growth is also thought to contribute to late lower incisor crowding into middle age.
 Research clearly shows that the likelihood of maintaining acceptable lower incisor alignment
in the long-term is extremely low (<30%) in orthodontically treated and untreated subjects.
 Continuing differential mandibular growth into adulthood is likely to contribute to these
changes as the lower incisors have to retrocline to compensate for this growth.
 Retroclination results in a decrease in arch circumference and crowding.
Orthodontic stability

9.  Extremes of mandibular growth rotation, both in a clockwise or anti-clockwise direction, also
contributes to late lower incisor crowding.
 Other predisposing factors may include periodontal disease and soft tissue maturational
changes that may alter the position of soft tissue balance.
 It is likely that the role of third molars in contributing to late lower incisor crowding has been
overstated in the past as current evidence suggests no causal link.
Orthodontic stability

10.  As mentioned above, retention should be considered during the treatment planning stages.
 Most cases, with few exceptions, benefit from a period of retention.
 It is also important to follow certain orthodontic principles whilst undertaking treatment to
maximize post-treatment stability: (a) maintaining the lower archform, (b) maintaining the AP
position of the lower incisors, (c) retracting the upper incisors behind the lower lip in Class II
cases, (d) correcting the inter-incisal angle following deep bite correction and (e) achieving
good intercuspation (e.g. following crossbite correction).
Planning retention

11.  The majority of patients completing fixed appliance treatment will benefit from the long-term
retention to minimize relapse and late lower incisor crowding.
 There are no current evidence-based guidelines on the ideal retention regimen.
 The author currently advises all patients to wear removable retainers every night for the first
year and to cut down gradually to 2-3 nights/week indefinitely if long-term alignment is to be
guaranteed.
 Permanent retention should be planned in cases where the lower incisors have been
proclined, large spaces have been closed, impacted canines have been aligned, severe
rotations have been corrected and where there has been previous periodontal disease.
 Permanent retention can be effectively achieved with fixed retainers.
Planning retention

12.  A simple classification of orthodontic retainers is outlined in the following figure.
Retention appliances
(B) A classification of orthodontic retainers

13. Retention appliances

14.  Retainers can be classified according to whether they are removable, fixed or active.
 Removable retainers have the advantage that they are removable for oral hygiene measures,
however, adequate wear is dependent on good compliance.
 Fixed retainers have the disadvantage of impeding oral hygiene, but are not dependent on
patient compliance for wear.
 Active retainers are removable retainers that actively maintain inter-arch relationships during
post-treatment growth or actively correct minor irregularities in tooth position (e.g. Barrer
appliance).
Retention appliances

15.  The classic Hawley appliance consists of an acrylic baseplate with Adams clasps placed on the
first molars and a labial bow with U-loops.
 It can be used in both the upper and lower arches and has the advantage of being durable.
 Modifications exist including use of a labial bow with acrylic to maintain correction of
rotations, a reverse U-loop to improve canine control, and a labial bow soldered to the bridge
of the Adam clasps to minimize wirework crossing the occlusion and facilitate occlusal settling.
 The baseplate can be modified into a U-shape to minimize palatal coverage and improve
comfort and speech.
 An anterior bite plane can be included for maintenance of deep bite correction.
Retention appliances

17.  The Begg retainer is a modified version of the Hawley retainer that does not incorporate
Adams clasps and therefore allows greater molar settling.
Retention appliances

18.  Vacuum formed thermoplastic retainers (e.g. the Essix appliance) are popular because of
their high patient acceptability, good aesthetics, ease of manufacture and low cost.
 These retainers are not as durable as Hawley-type retainers.
Retention appliances

19.  Fixed retainers are commonly constructed from 0.0175-inch diameter multi-strand SS wire
that can be bonded with composite resin to the lingual surfaces of the lower incisors and
canines.
 They can also be used in the upper arch to maintain diastema closure and correction of severe
rotations, and also after alignment of impacted canines.
 Fixed retainers can be constructed at the chairside or in the lab.
 Their main advantage is that they are not dependent on patient compliance for wear.
 Disadvantages include difficulty with oral hygiene, localized relapse and decalcification
following partial debond.
 Bonded retainers should be supplemented with removable retainers, which can be worn if
breakages occur.
Retention appliances

21.  Active retainers can be used to correct and maintain inter-arch and intra-arch dental
relationships.
 A functional appliance can be used for the remainder of the growth period following Class II
and Class III correction.
 The appliance is worn on a night-only basis and helps to maintain alignment as well as incisor
correction.
 High-pull headgear can also be incorporated into an upper appliance to help control vertical
maxillary growth in Class II cases with an increased vertical dimension.
Retention appliances

23.  The Barrer spring retainer is an active retainer that can be used to correct minor irregularities
in incisor alignment.
 The teeth are sectioned and aligned on a working model and the appliance is constructed to
the corrected position.
 When it is inserted into the mouth, an active force is placed onto the teeth to be repositioned
until tooth movement is complete.
 Interproximal enamel reduction may be necessary to provide space for alignment.
Retention appliances

24. Thank you so much for your kind attention.